Prior art patent document published U.S. Pat. No. 3,704,813 discloses a gas valve for compressed gas cylinders that prevents refilling. FIG. 2 of this document discloses a cylinder valve with a shut-off device, a pressure relief device and a check valve preventing refilling of the cylinder. The shut-off and pressure relief devices are combined and open when a refilling flow of gas is applied. The check valve comprises a ball held at a position distant from its seat by means of spring finger detents. The combined shut-off and pressure relief devices comprise a pin extending out of the valve body for actuating the shut-off device. Upon an opening stroke beyond a predetermined limit, the movable closing member of the shut-off device contacts the ball and pushes it beyond its holding position distant from the seat. The ball is then freed and can cooperate with its seat to prevent refilling of the cylinder after the first use of the gas. FIG. 3 of this document discloses an alternative design where the pressure relief device is separate from the shut-off device, the principle of the check valve operated by the first opening of the shut-off device remaining the same. In both designs, the spring finger detents restrict the available cross area for the check valve spring. Additionally, under certain circumstances the assembling operations of the check valve might be rendered difficult in that the ball might tend to escape from its seat on the finger detents. Also, both designs require much space laterally.
Prior art patent document published US 2003/0029508 A1 discloses, similarly to the previous document, a gas valve for compressed gas cylinders that prevents refilling. The passage in the valve body is generally cylindrical and comprises on its internal surface detents like a pair of diametrically opposed dimples extending towards each other. The ball of the check valve rests therefore on these detents as long as the pin of the shut-off device does not push it past the detents. The body is in principle made of metallic material and the drawings show that the detents are intended to be made by plastic deformation of the valve body on its external surface. The ball must therefore be resilient enough for being able to pass beyond the detents when urged by the shut-off device pin. To that end, the ball can be made of elastomeric material. The use of such a material can cause problems with the reliability of the check valve and its compatibility with high pressures. The effort necessary for having the ball passing the detents might be high and cause some difficulties for the persons manipulating the cylinder. Additionally, even though the assembly appears to be quite easy, the shut-off device is a valve core that is screwed into the passage of the body. This means that this design requires some space laterally and also might increase the production costs.
Prior art patent document published US 2004/0144803 A1 discloses a non-refillable valve including a body, a gas inlet, a gas outlet and a passage connecting the outlet with the inlet. The valve comprises also a shut-off device of the passage with an actuating pin extending in the passage. The pin comprises a shoulder portion bearing a first circular gasket that cooperates with a seat in the passage, so as to close the passage. The valve comprises also a second circular gasket fixed to the body around the gas passage downstream of the seat cooperating with the first circular gasket. The pin is able to slide in a gas tight manner along the second circular gasket. The pin comprises an axial central bore opened on the outlet side of the valve and a radial aperture connecting the central bore with the passage between the first and second gaskets. The gas passage comprises also upstream of the shut-off device an axially extending internal chamber. A plug member is secured within the chamber to provide a fluid flow passage between the container and the body chamber when the body is secured to the container, and an elastic sealing member is also disposed within the chamber. The sealing member is displaceable from a first position to a second position within the chamber, where the sealing member in the first position permits fluid flowing for refilling the container, i.e. from the outlet to the inlet of the valve, and the sealing member in the second position substantially prevents fluid flow in the refilling direction. The valve pin is configured to mode the sealing member from the first position to the second position. This valve is interesting in that it has a reduced number of parts and provides an anti-refilling function. It has however the drawback that the first gasket movable with the pin come into contact with a potentially sharp angle of the seat. This results from the relatively simple construction of the pin.